The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A variety of intrusive and non-intrusive pressure sensing means are known for sensing pressure within an internal combustion engine cylinder when the engine is motoring and during engine firing.
Various aspects of internal combustion engine controls are known which rely on in in-cylinder pressure measurements, particularly location of peak pressure (LPP), indicated mean effective pressure (IMEP) calibration and absolute peak pressure.
Diesel engine noise is known to be objectionable. It is also known that some relief is provided by pilot injection techniques. However, precise pilot injection remains challenging and known systems may exhibit unacceptable variability.
Known systems employ a noise-detecting procedure using signal information from block-mounted accelerometers to sense block vibration. The primary deficiencies of the existing systems relate to robustness and accuracy of the corrections.
It is known that multiple fuel injections per cylinder event are desirable in compression-ignition engines to alleviate undesirable combustion characteristics and attributes thereof, including e.g., noise. In such situation, the control system executes a pilot injection prior to a main fuel injection event to preheat the combustion chamber. In such systems, the pilot injection comprises a minimal amount of fuel, preferably injected at or near about top-dead-center (TDC) of piston travel, with the main fuel injection occurring after TDC, depending upon the engine load.
Reliably and accurately delivering pilot fuel is challenging for many fuel systems, and a method for detecting effects of the pilot injection and adjusting the injection during ongoing operation is desirable. Cylinder pressure transducers may enable fine tuning of the pilot injection. However, relatively high data sample rates are typically required.
Hence, a method is described herein which provides a high level of accuracy and alleviates issues related to use of calibrated pressure sensors. This makes it adaptable to methods for control systems with cylinder pressure sensors that are not calibrated.